It started with Joy Beeson's question:
[...] the standard-issue human has three
color receptors. We call this sort of vision trichromatic. If one of the
receptors is missing or defective, we say "color blind", but he isn't
really, he's dichromatic.
A truly color-blind person would have only one functioning set of cones.
(Is there such a thing as a "dayblind" person who has no cones at all, and
has to get by on the rods?)
Lynn Carpenter answered:
The word for rods-only vision is "achromatatopsia". More info at: http://www.achromat.org/
Here is a first-hand account by an achromat:
http://www.u.arizona.edu/~chalmers/misc/achromat.html
Although I only skimmed through the bits and pieces of the first website (enough to learn that total colour-blindness, in US, happens to 1 in 33 thousand <g>), I read the account on the second site in full. It's long, and text-reading from the screen is not an easy thing for me, but it was fascinating enough to keep me going (thanks, Lynn, for digging it up!).
The man who relates his experience has other vision problems in addition to the achromatopsia, but, distilling even from his account, a colour code ought to be possible for him to read, as long as the use of colour was limited (which is what I said to begin with <g>). Having both physics and art training, he calls it "saturation", where I think of "density", but he can (in addition to black and white) distinguish dark-grey (red falls into that category for him), medium-grey (blues and greens), and light-grey (he can tell yellow from white, for example).
So. If we used just three (which is all that's really needed, if one uses other "means" to supplement) colours in our diagrams, even a *totally* colour-blind person could follow them...
Red (interpreted as "dark grey") = cloth stitch (CTC, or \ // \) (where // means twisting both pairs at once -- a "turn") --
Red + cross-hatch = whole stitch (CTCT, or \ // \ //)
Green/blue/turquoise (interpreted as "medium grey") = half stitch (CT, or \ //) and, with cross-hatches and the zig-zag fro plait, just about every other stitch or stitch combination)
Yellow for single thread.
Pattern designers and printers both would love it; the permissible leeway in the *shade* of each colour would be much greater ("my" Xerox-lady used to apologise *all the time* for the inexact reproduction), without being misleading. Colour-blind people could decipher it. Colour-happy people could see -- at a glance -- where they could "gallop", and where they had to slow down to a stitch-by stitch, cautious, "walk".
Though I agree with Carol (Adkinson) that, *first*, the differently-coloured lines would have to *meet*, and meet at the right places; they're useless otherwise :) But, I think the discrepancies are due to printers using different plates for each colour; with other technology (and means of reproduction) being used more frequently now, that problem is likely to disappear, eventually.
PS. I found it of particular interest that the sister of the man who describes his achromatic life is an embroiderer, a tatter, and a bobbin-lacemaker. She, like his other sibling (a brother) shares all his visual burdens, including the colour-blindness. He does not say whether she uses colour-coded diagrams for her BL, though :)
----- Tamara P Duvall Lexington, Virginia, USA Formerly of Warsaw, Poland http://lorien.emufarm.org/~tpd/
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